YOU SAID:

I ain't never seen two pretty best friends, it's always one of 'em gotta be ugly.

INTO JAPANESE

私は2人のかわいい親友を見たことがない、それは常に醜い必要があります。

BACK INTO ENGLISH

I've never seen two cute best friends, it must always be ugly.

INTO JAPANESE

私は2人のかわいい親友を見たことがない、それは常に醜いに違いない。

BACK INTO ENGLISH

I've never seen two cute best friends, it must always be ugly.